This invention relates to controlled fragmentation explosive devices. More particularly the invention relates to explosive devices having control over the size and shape of fragments produced by the device.
To avoid random distribution of fragments propelled by exploding anti-property and personnel devices, it is necessary to control the size, shape, and weight of the fragments. Small fragments have low mass and will not possess optimum amount of kinetic energy against a desired target compared to a larger mass fragment traveling at the same velocity. Large fragments, and in particular, bar, plate, and diamond shapes, however, offer more atmospheric drag causing the fragment velocity to slow down rapidly, resulting in a reduced kinetic energy on the target. It can be appreciated that inconsistant fragment size, shape and weight are undesirable.
Heretofore, fragmentation control has included providing grooves on either the external or internal surfaces of the wall of the case or a liner inserted into the case. The grooves create stress concentrations that cause the case to fracture along the grooves forming fragments. Generally these grooves are longitudinal, circumferential, or both, or constitute a series of intersecting helical grooves designed to produce diamond shape fragments. While these devices have demonstrated the ability to create fragments, they are not completely satisfactory for several reasons.
First, the fragments are often much smaller than they ordinarily should be due to fragment weight loss during the fragmentation process. Allowance for weight loss requires that the device be designed to produce larger fragments than will actually result. This reduces the number of fragments available for a given warhead.
Second, the prior art devices produce fragments of a variety of weights and do eliminate the variations in kinetic energy resulting therefrom. Additionally, diamond shaped fragments have high drag coefficients, which as stated, result in rapid decay of fragment velocity.
Casings that are relatively thick are susceptible to producing fragments of varying shapes and weights. The helical grooves heretofore utilized are ineffective in controlling these fragment variations.
Finally, during the fragmentation process much energy is wasted on metal deformation. Frequently, the corners of the fragments are turned up which further increases drag. It is desirable to provide the device with means for increasing the amount of energy directed to fragmentation rather than being wasted in fragment deformation.